1. Chemical and Physical Bases of Life
Lecture 1
Feb 26, 2018

2. Learning Objectives List the attributes of living organisms
Describe the features of compounds, acids, bases, and salts
List the chemical elements found in cells
Understand the properties of water

3. Biology is the Study of Life
Greek and Latin root for Biology
Bi(ola) = life
log(y) = discourse, the study of
What defines something as alive?
The ability to assimilate and use energy
The ability to respond to their environment
The ability to maintain a relatively constant internal environment
Have evolved from other living things
The ability to reproduce
Composed of one or more cells with information encoded by DNA
Are highly organized when compared to inanimate objects
The ability to grow and develop
Non-living objects are not self-sustaining
Inanimate
Assimilate = to take in and incorporate into one’s own body

4. Characteristics of Living Things
Living organisms use energy

5. Characteristics of Living Things
Living organisms respond to their environment

6. Characteristics of Living Things
Living organisms maintain homeostasis or some relatively constant internal environment
A stated in Wikipedia “Homeostasis is the property of a system within an animal in which a variable, such as the concentration of a substance in solution, is actively regulated to remain very nearly constant.[1] Examples of homeostasis include the regulation of body temperature, the pH of extracellular fluid, or the concentrations of sodium, potassium and calcium ions, as well as that of glucose in the blood plasma, despite changes in the environment, diet, or level of activity. Each of these variables is controlled by a separate regulator or homeostatic mechanism, which, together, maintain life.”

7. Characteristics of Living Things
Living things have evolved from other living things

8. Characteristics of Living Things
Living organisms reproduce

9. Characteristics of Living Things
Living things are composed of one or more cells
Humans comprised of 10 trillion cells
Amoeba is a single celled organism

10. Characteristics of Living Things
Living organisms contain DNA
Inherited information base that codes for everything!

11. Characteristics of Living Things
Living organisms are highly organized compared to inanimate objects

12. Characteristics of Living Things
Living organisms grow and develop

13. Matter, Mass, and the Atom
Matter: anything that takes up space and has mass
Mass: measure of the quantity of matter in a given object
Volume and density
An atom is the smallest stable subdivision of an element that can exist.
Atoms are indivisible.
Indivisible: cannot be broken down further
Atoms are the fundamental unit of matter
Can’t be subdivided any further without losing its essential properties.

14. The Atom Atoms are made up of three subatomic particles:
Protons: component of the atom’s nucleus with a positive electrical charge.
Elements are defined by number of protons.
Neutrons: component of the atom’s nucleus with NO electrical charge.
Isotopes are defined by number of neutrons.
Electrons: located some distance from atom nucleus and has a negative electrical charge.
Protons
No electrical charge

15. Structure of the Atom electron shell nucleus Hydrogen (H) Helium (He)
neutron
(no charge)
proton
(positive charge)
(negative charge)

16. Elements
Element: a substance that can not be reduced to a more simple set of components through chemical processes.
Elements are pure forms of chemicals consisting of a single type of atom
Currently 98 elements have been discovered that are present in nature and ~20 others can be made in the lab.
*Carbon, Oxygen, Nitrogen and Hydrogen make up 96% of human body mass

17. Molecules: Combinations of Elements
Molecule: two or more atoms together
Ex. O2
Compound: two or more elements together
Ex. H2O
molecule

18. Elements in the Human Body
Only 10 elements make up 99% of the human body. Four of these ten elements (oxygen, carbon, hydrogen and nitrogen) making up around 96% of your body 10
carbon

19. Understanding the Elements
Atomic number: number of protons in the atom’s nucleus
Elements differ in the number ofprotons in their nucleus
Element symbol: abbreviation of element’s name
Atomic mass: combined mass of atom’s protons and neutrons
# of protons in their nucleus
Atomic mass:
Neutron = 1
Proton = , 99.86% mass of neutrons
Electron = , 0.054% mass of neutrons 3
Atomic number
Element symbol
Element name
Atomic mass Li
Lithium
6.941

20. Check Your Understanding
What is the elemental symbol for sodium?
How many protons are found in the nucleus of calcium?
What is the average combined mass of the protons and neutrons in Lithium?

21. Isotopes
Isotopes: a form of an element as defined by the number of neutrons contained in the nucleus

22. Electron Energy Levels
Electrons (e-) orbit atom nucleus at different energy levels (shells)
1st shell = 2 e-
2nd shell = 8 e-
3rd shell = 8 e-
And so on…
Atoms with vacancies in their outermost electron shell are more reactive, whereas atoms with full shells are more stable.
More reactive and less stable
More stable and (neither reacting nor combining with other atoms)

23. Electron Energy Levels
Inner shell
Electron
Electron shell
Nucleus
Outer
(valence)
shell
Hydrogen 1 H
Carbon 6 C 12
Nitrogen 7 N 14
Oxygen 8 O 16

24. Check Your Understanding
1. Draw the structures for a calcium and chloride atom. Be sure to include the correct number of electrons in the outer most shell.
Calcium has an atomic number of 20 and chloride has an atomic number of 17

25. Check Your Understanding
2. How many electrons are found in a sodium atom? Hint: The atomic number for sodium is How many neutrons are found in the nucleus of the isotope Oxygen-18? Hint: The atomic number for oxygen is 8.

26. Making Stable Compounds
Atoms bond together to complete outer shell electrons
Fill

27. Types of Chemical Bonding
Covalent bonding: when two atoms share pairs of electrons
Non-polar covalent bond: when a covalent bond results in a nonpolar/symmetric molecule
Ex: Carbon dioxide = CO2
Polar covalent bond: when a covalent bond results in a polar molecule
Ex: Water molecule = H2O
Polarity: a difference in electrical charge on opposing ends of molecule
Share
Non polar
Polarity
** when one pair of electrons is shared, the bond is said to be single (like in H-H). When two pairs of electrons are shared , the bond is referred to as double (like in C=C), and triple bonds are formed when three pairs of electrons are shared.

28. Types of Chemical Bonding
Ionic bonding: when one atom transfer an electron to another atom, with resulting ions become linked by attraction of opposing charges
After gaining or losing an electron, atoms become charged (ions)
Ion: a charged atom; number of electrons does not equal number of protons
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
# of electrons does not equal # of protons
Cation: a positively charged ion
Anion: A negatively charged ion

29. Types of Chemical Bonding
Hydrogen bonding: covalent bond between hydrogen atoms and an electronegative atom
Bound by attraction of electrical charge
Relatively weak bonds
Weak

30. Summary of Molecule Bonding
Covalent bonding: a bond formed between two atoms that share electrons
Bond strength : Strong
Ionic bonding: a compound that is formed by the attraction of two oppositely charged ions
Bond strength: Strong
Hydrogen bonding: a bond formed between the slightly positively charged hydrogen atom and the slightly negatively charged region of another atom
Bond strength: Weak

31. The Amazing H2O Water is essential to life Life started in water
Terrestrial life depends of water
Cells immersed in water
66% of our body weight
Water has unique properties that allow life to exist on earth

32. Hydrogen bonds of water molecule pull other compounds apart
Properties of Water
The Universal Solvent
Water can dissolve more substances than any other liquid
Solute: substance being dissolved to form a solution
Solvent: substance that a solute is dissolved in to form a solution
Aqueous solution = water is the solvent
Solution: a homogeneous mixture of two or more substances
Hydrogen bonds of water molecule pull other compounds apart
Dissolved
Liquid

33. Properties of Water Water is a polar molecule
Polarity of water molecules works to pull apart ions
Partial negative charge
Polarity of water molecules
Partial positive charge

34. Properties of Water Liquid form is denser than solid form
Ice floats on water!
more dense
**water becomes less dense due to hydrogen bonds. As the temp. drops and water molecules slow down, each water molecule bonds with four partners via hydrogen bonds forming a crystalline lattice in which the molecules are held slightly farther apart than in the liquid --- less dense ice
Note: Most substances increase in density when frozen. As the cooling molecules slow down, they pack together more efficiently and densely.( the solid sinks)

35. Properties of Water
Cohesion: the tendency for like molecules to cling together due to attractive forces
Cohesion

36. Properties of Water
Surface tension: water molecules are not attracted to air and pack more tightly at interface

37. Properties of Water
Specific heat: amount of energy required to raise temp 1˚C
Water has a high specific heat compared to other molecules
Water acts as buffer to temperature changes
Moderator
Reason why desert experiences such extreme temperature changes. Little water vapor fails to capture heat from day so desert nights are very cold.

38. Properties of Water High heat of vaporization
Vaporization: transformation from liquid to gas
Fastest moving water molecules transform to a gaseous state.
Sweat helps release internal body heat
Evaporative cooling: cooling of surface when liquid evaporates
Liquid to gas
High heat of vaporization means that a lot of energy I required to transform water from a liquid to a gas due to the strength of the hydrogen bonds. Boiling point of water 100C or 212F

39. Molecular Attraction to Water
Hydrophilic (“water loving”): compounds that will interact with water
Ex. Sodium Chloride (NaCl)
Hydrophobic (“water fearing”): compounds that do not interact with water
Ex: Hydrocarbons (petroleum, oil) and lipids (fats)
Hydrophobic molecules help contain water
Hydrophobic
Cell membrane

40. Acids and Bases
Acid: substance that donates hydrogen ions in an aqueous (water-based) solution
Hydrogen ion = lone proton H+
Base: substance that accepts hydrogen ions in an aqueous solution
Hydroxide ion = Oxygen and Hydrogen OH-
Alkaline = basic solution
Has more H+ and fewer OH-
Has fewer H+ and more OH-

41. Acids and Bases A B C Pure H2O, pH = 7 Making water more acidic
Hydrochloric acid (HCl)
+ H2O, dissociates into H+ and Cl– ions. pH = 4
Making water
more basic
sodium hydroxide (NaOH) + H2O dissociates into Na+ and OH– ions. pH = 10 B C
Combining acidic and basic solutions
When poured together, the OH– ions from (C) accept the H+ ions from (B), forming water and keeping the solution at a neutral pH.
H+ + OH–  H20
acid base neutral solution

42. Acids and Bases pH Scale : measures (p)ower of (H)ydrogen
Logarithmic scale (base 10)
pH = more basic (8-14)
pH of 7 = neutral
pH = more acidic (6-0)
Dr. Søren Sørensen developed the pH scale to measure acidity of beer
The lower the number of pH the greater the acidity; a decrease of 1 on the pH scale represents a 10-fold increase in the hydrogen ion concentration. A decrease of 2 represents a 100-fold increase.

43. Acids and Bases
The burning of fossil fuels releases sulfur dioxide and nitrogen dioxide
Sulfur dioxide and nitrogen dioxide combine with atmospheric water to form sulfuric acid and nitric acid
Acids fall to earth as acid precipitation
Clean air act amendments designed to curb acid rain